1. Field of the Invention
The present invention relates to a display apparatus and a driving method thereof, and more specifically, to an organic light emitting diode device and a driving method thereof
2. Discussion of the Background
Recently, research has been conducted into flat display devices that are capable of replacing cathode ray tube (CRT) display devices. One type of flat display apparatus, the organic light emitting diode (OLED) device, has a wide viewing angle and high quality brightness. Therefore the OLED device is being developed as a next generation flat display device.
In active matrix flat display devices, a plurality of pixels may be arranged along rows and columns of a matrix, and an intensity of light emitting from the pixels may be controlled according to information signals. When the information signals are transmitted to the pixels, light with a brightness corresponding to the data in the information signals is emitted from a plurality of pixels on the flat display device. From a viewer's perspective, the light coming from the flat display device forms an image. The OLED device is a display device that electrically excites phosphorous organic electroluminescent materials to emit light, thus forming an image on the display device. As a self-emitting apparatus with low power consumption, a wide viewing angle, and a high response speed, the OLED device can display a high quality moving image.
The OLED device includes organic light emitting diodes (OLEDs) and thin film transistors (TFTs) that control the signals driving the OLEDs. A TFT may be classified as a polysilicon TFT or an amorphous silicon TFT according to the type of active layer in the TFT. Due to several advantages, OLED devices employing the polysilicon TFTs have been generally used. However, manufacturing processes for polysilicon TFTs can be complex, and thus, production costs may increase. In addition, it may be difficult to manufacture a large display device by using the OLED devices with polysilicon TFTs.
By using the OLED devices with amorphous silicon TFTs, a large screen may be more easily obtained. In addition, the number of production processes for the manufacture of an OLED device with amorphous silicon TFTs may be fewer than the number of production processes for an OLED device with polysilicon TFTs. However, because amorphous silicon TFTs in a pixel may continuously supply a current to the pixel's OLED, the threshold voltage of an amorphous silicon TFT may deteriorate. Further, even though a single data voltage may be applied, a deteriorated threshold voltage may result in non-uniform current flowing to the OLED in the pixel, so that the image quality of the OLED device may deteriorate.
The above information disclosed in this Background section is provided for the sole purpose of enhancing the understanding of the background of the present invention. Therefore, this Background section may contain information that does not form the prior art known in this country to a person of ordinary skill in the art.